A standard four-high rolling stand of the type used for rolling strip steel has a pair of vertically spaced nip-defining working rolls of relatively small diameter. Respective upper and lower backup rolls of larger diameter bear respectively down and up toward the nip on the respective working rolls. Thus the bendability of the small-diameter working rolls is largely canceled out by the rigidity of the larger-diameter backup rolls so that the large forces required for rolling can be brought to bear on the workpiece.
As described in German patent document No. 1,777,054 filed June 28, 1966 by K. Leifeld and E. Stoy and in German patent document No. 3,212,070 filed by H. Ishikawajima with a claim to a Japanese priority of Apr. 2, 1981, roll stands are known wherein the working rolls are driven by the backup rolls and one of them is centered on an axis offset from the plane of the backup rolls and the other working roll, typically downstream therefrom relative to the workpiece travel direction.
In these arrangements the roll ends can be twisted to horizontally and vertically bend the working rolls in an effort to cancel out the inward bending of the rolls that normally results during rolling. The intent is of course to produce a workpiece of perfect surface planarity and uniform thickness, as described in copending and commonly owned patent application Nos. 352,520 filed Feb. 26, 1982 by W. Bald, Ser. No. 558,165 filed 12-5-83, filed by H. Rommen et al, and Ser. No. 555,458 filed 11-28-83, filed also by H. Rommen et al. German patent document No. 2,522,213 filed May 17, 1975 by H. Rommen and E. Stoy further describes such an arrangement that achieves a complex three-dimensional bending of one of the working rolls. This structure also is enormously complicated and hard to control.
In the arrangement with an offset working roll the offset roll is substantially smaller in diameter than the one that is coplanar with the other rolls. This therefore also complicates the construction of the equipment.